Modulating hydration chemistry of GO/CSH antibacterial hydrogel evaporator toward high-efficiency solar-driven interfacial desalination

Abstract

Solar-driven interfacial desalination (SDID) is regarded as a low-cost, environmentally friendly, and sustainable technology for clean water production, contributing to the global decarbonization. However, it remains challenging to achieve high evaporation rate in high-salinity brines and avoid bio-fouling issues. Herein, an antibacterial hydrogel solar evaporator (AHSE) with outstanding hydratability is developed by cross-linking graphene oxide‑calcium silicate hydrate (GO-CSH) with polyvinyl alcohol (PVA) and N-(phosphonomethyl) iminodiacetic acid decorated polyethyleneimine (PMIDA-PEI) for high-efficiency SDID. The AHSE manifests orderly aligned porous structure with uniformly loaded GO-CSH as hydrophilic channel, improving the capillary-wicking ability of microchannels for rapid water replenishment. Theoretical calculations reveal that the hydration chemistry of AHSE can be enhanced due to the weakened hydrogen bond interaction between CSH and polymer networks, thus benefiting the exposure of hydratable sites for a decreased vaporization enthalpy. As a result, an evaporation rate of 3.25 kg m⁻² h⁻¹ and an energy conversion efficiency of 95 % under one sun irradiation are achieved in 25 wt% brine without salt accumulation. In addition, AHSE exhibits excellent antibacterial activity, as well as the antifouling functionality, guaranteeing the durability of evaporator and freshwater safety in practical applications. This work provides novel insights into the design of high performance solar-driven evaporators at a molecular level.